Lubricating oil composition containing a silicon-tin-containing compound



LUBRICATING OIL COMPOSITION CONTAINING A SlLICON-TIN-CONTAINING COMPOUNDNorman G. Holdstock, Scotia, N.Y.,- assign'or to General ElectricCompany, a corporation of New York No Drawing. Filed Dec. 11, 1957, Ser.No. 701,956

Claims. (Cl. 252-49.7)

This invention relates to lubricants. More particularly it relates toliquid lubricants which are characterized by desirable lubricity at hightemperatures and to the preparation of such lubricants.

it is well known that while many naturally occurring mineral andvegetable oils have good lubricating qualities and stability at lowertemperatures, at a critical higher temperature the coefiicient offriction of these materials rises sharply denoting the loss of theirlubricity. It has been suggested that oils of the organopolysiloxanetype be substituted for the natural oils for higher temperature uses andthis has been done with some success. These organopolysiloxane materialsare characterized by outstanding resistance to heat and oxidation atelevated tem perature, have low viscosity-temperature coefficients andlow pour points. Many of these organopolysiloxane materials are thosewhich one obtains from the hydrolysis or cohydrolysis and condensationof the varioussubstituted silanes. Lubricants of this general type areset forth, for example, in Patents 2,469,888, 2,469,890, and 2,689,- 859among others, assigned to the same assignee as the present invention andalso in Patent 2,599,984, the teachings of which are included herein byreference.

While such liquid organopolysiloxanes have been found to be very usefulas lubricants at temperatures up to about 400 F. under varying loads,with further rise in temperature the coefficient of friction of thesematerials rises sharply rendering the material of limited if anyusefulness at temperatures above the order of 400 F. The loss oflubricity is more aggravated, of course, at higher loads. There is aload and temperature for each such lubricant at'which its lubricity islost. With the continued development of power plants such as internalcombustion engines, gas turbine engines, aircraft power plants and otherequipment which operate at temperatures of the order of up to 700 F. andhigher, the need for lubricants and hydraulic fluids which will retaindesirable qualities at such temperatures is quite apparent.

A principal object of this invention, therefore, is to providelubricating materials which have desirable lubricating qualities attemperatures of the order of 700 F. and higher.

Briefly stated the invention comprises the hydrolysis and condensationproducts of organopolysiloxanes or other natural or synthetic materialsin combination with organopolysiloxanes containing tin, carbon andsilicon units which later may be characterized by the following formula:

wherein R and R are various organic groups as described more fullyhereinafter and n is a number from about 1 to 1000 and preferably'fromabout to 40.

tent

novel are set forth with particularity in the appended claims. Theinvention, however, both as to its organization and method of operation,together with further objects and advantages may better be understood byreference to the following description.

The liquid organo-substituted polysiloxanes with which this invention isconcerned are compositions comprising essentially silicon atomsconnected to one another by oxygen atoms or a siloxane structure whereina preponderant number of the valences of the silicon atoms are satisfiedby the substitution thereon of organic radicals, for example, aliphaticradicals. These compositions of matter can typically be prepared byhydrolysis of hydrolyzable aliphatic-substituted silanes, for example,dialiphatic dihalogenosilanes such as dimethyldichlorosilane followed bycomplete or partial condensation of the hydrolysis product. They canalso be prepared, by hydrolyzing mixtures of hydrolyzablediorgano-substituted silanes either with themselves or with hydrolyzablesilanes containing, for example, three organic radicals substituted onthe silicon atom, for instance, trimethylchlorosilane.

A further method for preparing the liquid organo-sub? stitutedpolysiloxanes comprises hydrolyzing a diorganojsubstituteddihalogenosilane, isolating the hydrolysis product and efiectingreaction between the hydrolyzed product and, for example, hexamethyldisiloxane in the presence of sulfuric acid. More specific directionsfor the hydrolysis of hydrolyzable organo-substituted silanes to formliquid organo-substituted polysiloxanes can be found in various patentsand in the literature now available in the art.

By the term hydrolyzable organo-substituted silanes are meantderivatives of SiI-l, which contain hydrolyzable groups or radicals, forexample,halogens, amino groups, alkoxy, aryloxy, and acyloxy radicals,etc., in addition to I the organic groups substituted directly on thesilicon atom that are joined to the silicon through carbon-siliconlinkages. Examples of such organic radicals are aliphatic radicalsincluding alkyl radicals, for example, methyl, ethyl, propyl, isopropyl,butyl, etc.; alicyclic radicals, for example, cyclopentyl, cyclohexyl,etc.; aryl radicals, for example, phenyl, diphenyl, naphthyl, anthracyl,etc.; aralkyl radicals, for example, benzyl, phenylethyl, etc.;

alkaryl radicals, for example, tolyl, xylyl, etc.; heterocyclicradicals, etc.; as well as hydrolyzable silanes coritaining twodifferent organic radicals, for example, methyl and phenyl radicals,etc., attached to the silicon atom. If desired, the above-mentionedradicals can also contain substituents substituted thereon, forinstance, halogens, e.g., di-, tri-, tetrachlorophenylchlorosilanes, forexample, trichlorophenyltrichlorosilane,tetrachlorophenyltrichlorosilane, etc.

Hydrolysis of the above silanes or mixtures of silanes results in theformation of silanols, i.e., organo-substituted silanes containinghydroxy groups substituted directly on the silicon, which hydroxy groupsalmost immediately condense intermolecularly (intercondense) splittingout water to give the siloxane linkages mentioned previously. Suchintercondensations are accelerated by acidic materials, for example,sulfuric acid, hydrochloric acid, ferric chloride, etc., as well as bybasic materials, for example, sodium hydroxide, potassium hydroxide,etc. As a result of the hydrolysis and condensation, liquidorgano-substituted polysiloxanes can be produced which are partially orcompletely condensed and which may have on the average up to as high asthree organic radicals substituted per silicon atom, but preferably from1.98 to 2.25 organic groups per silicon atom. The liquidorganopolysiloxanes prepared in this manner consist essentially ofsilicon atoms joined together by oxygen atoms through silicon-oxygenlinkages and organic radicals attached to silicon through carbon-siliconlinkages, the remaining valences, if any, of the silicon atoms beingsatisfied by hydroxyl radicals and/or by residual unhydrolyzed radicalssuch as the hydrolyzable radicals listed previously.

In accordance with the invention it has been found that thefrictionalproperties at elevated temperatures, that is from about 200 F. to 400 F.and higher of liquid organo-substituted polysiloxanes, especially thosecontaining aromatic nuclearly substituted halogen, such as chlorine andhaving an average of from about 1.98 to 2.25 organic groups per siliconatom can be substantially improved by incorporating in the liquidpolysiloxanes small amounts of certain tin-carbon-silicon compounds.

As pointed out above the tin-carbon-silicon compounds of the presentinvention may be expressed by the formula having the general structure Ll. l i i ll.

where R and R are aliphatic radicals including lower alkyl radicals suchas methyl, ethyl, propyl, isopropyl, butyl, etc.;- alicyclic radicalssuch as cyclopentyl, cyclohexyl, etc.; aryl radicals such as phenyl,diphenyl, naphthyl, anthracyl, etc.; aralkyl radicals such as benzyl,phenylethyl, etc.; alkaryl radicals such as tolyl, xylyl, etc.;heterocych'c radicals and mixtures of the above in the case of R, theabove mentioned radicals also containing, if desired, substituents suchas halogens, e.g., chlorophenyl, etc.; and n is a number from about 1 to1000 and preferably from about to 40.

The tin-silicon compounds may be conveniently prepared through thereaction of the Grignard of haloalkyl siloxanes and diorgano tindihalides. The following examples illustrate the preparations ofsuch'rnaterials, it

being realized that other methods of such preparation will occur tothose skilled in the art.

EXAMPLE 1 To 8grams of magnesium and diethylether there was added 35grams of bischloromethyltetramethyldisiloxane slowly after the reactionhad been started with heating and a small amount (0.5 cc.) of ethylbromide. When the reaction has ceased, practically all the magnesium OH:H Chis l where n is equal to about 20.

EXAMPLE 2 This example is the same as Example 1 except that the Grignardreagent was reacted with triphenyl tin chloride to give a compoundhaving the following structure In general it has been found thatcompounds of the described type of Example 1 above in which n is equalto from about 15 to 40 are most useful in connection with thisinvention, it being realized that compounds having a lower 11 value maybe used, taking into consideration that their volatility will result inloss of material. Compounds having an :1 value up to about 1000 havealso proved useful. Generally, it has been found that amounts of thetin-silicon compound ranging from about 1.0 to about 10% by weight ofthe additive based on the weight of the base lubricating material areuseful in improving the oxidation resistance, lubricity and loadcarrying ability of the lubricant. Preferably about 3 to 5% of theadditive is used. In general, amounts over 3% while not deleterious donot improve the character istics of the lubricant. Of course, amountsless than 1% will also give some improvement.

The following examples will illustrate the practice of the presentinvention. The organopolysiloxane fluid used in the examples was amethylchlorophenylpolysiloxane chain stopped with trimethylsilyl groupsand having intercondensed dimethyl-siloxy groups and chlorinatedphenyl-siloxy groups, there being present an av erage of about fourchlorine atoms on each phenyl nucleus and the molar concentration ofsilicon-bonded chlorinated phenyl groups being of the order of about 4.4mol percent. This fluid was heated to 300 C. at 5 mm. of mercury with anitrogen sparge and all volatiles boiling up to that temperature wereremoved. The viscosity of the devolatilized oily liquid wasapproximately 60 centistokes at about 50 C.

EXAMPLE 3 A methyl chlorophenylpolysiloxane as above was tested forstability to oxidation by heating to a temperature at which oxidationbecame apparent and further to a temperature at which gelation tookplace. When the organopolysiloxane was heated alone, the thresholdtemperature or the temperature at which oxidation began was 430 F. andthe time to gelation at 600 F. was 10 minutes. When there was added tothe above organopolysiloxane 3%, by weight, of the tin-siliconcarbonorganopolysiloxane of Example 1 above, the threshold temperature rosedeg. F. to 510 deg. F. and the time to gelation at 600 deg. F. was 45minutes.

The apparatus used for testing the lubricating qualities of theorganopolysiloxanes described herein is the socalled Shell 4 ball weartester. This testing device consists essentially of three steel balls,each about $6 in diameter, clamped securely in the non-rotating fashionin a cup with a fourth ball mounted in a rotatable chuck and adapted tospin in the cavity formed by the three adjacent balls. A loading arm isutilized to force the cup containing the balls against the chuck, theload being varied in any manner desired. Provision is made for holdingthe lubricant to be tested in the cup containing the balls so that thelatter are continually immersed in the lubricant. In testing alubricant, the apparatus is heated to a temperature desired and thechuck and top ball rotated for a given period of time at a particularnumber of revolutions per minute under a fixed load.

After the test is completed, the lower or fixed balls are examined witha microscope and the size and sear worn in them by the upper rotatingball noted and taken as a measure of the comparative lubricating qualityunder the particular set of conditions. The average diameter of thegenerally circular scar is used. In the tests described below, thespindle speed of the apparatus was 600 revolutions per minute except asotherwise stated and the time for each test run was 2 hours.

Shown in Table I is a comparison between the exemplaryorganopolysiloxane described insofar as its lubricating qualities areconcerned as tested on the 4 ball tester, with the same material towhich has been added 3%, by weig t 05 the material of Example 1 above.

Table I Table IV Spindle Scar (mm.) Scar ('mm.) Spindle Temper- LoadScar 7 Speed Load (kg) Temp. Untreated Treated Speed ature (kg) (mm.)Material (r.p.m F.) Organopoly- Organopoly- (r.p.m.) F.)

siloxane siloxane 212 40 97 Organopolysiloxane. 4 212 .42 .37 212 40 .94Diester blend [di-(2 ethyl- 10 212 47 54 hexyl) sebaeate]. 40 212 1. 1080 212 40 90 Light Mineral oil. 50 212 2. 19 l. 00 212 40 98 MineralOil.

4 400 58 52 212 40 1.10 Dimethyl silicone oil. 10 400 .61 .54 40 4001.70 .90 I 50 $90 l-gg The above data demonstrates that the presentinveni3, tion is useful not only in conjunction with organopoly- 40 400-7 siloxanes but, surprisingly, with other types of lubricants 40 7002.70 1.80 as Well The superiority of the present materials at elevatedtemperatures is at once evident from the above. The load carryingcapacity of the various lubricants, treated and untreated, was measuredby stabilizing the sliding velocity, the temperature, test pieces andtime intervals with the load gradually being increased until a sharprise in the coeflicient of friction was noticed. This indicates thatthere has been a sudden change in the condition of the sliding surfaceand generally means than the lubricant has approached a point of failureor a so-called transition point. Shown in Table II below, are thetransition loads for various temperatures and spindle speeds for theabove organosiloxane material untreated and containing 3%, by weight, ofthe tin-silicon material of Example 1.

Keeping the load and speed constant and varying the temperature, thetransition temperatures as shown in Table III were determined for a loadof 40 kg.

Table III Transition Transition Spindle Speed Temp. F.) Temp. F.)

(r.p,m.) Load (kg) (Untreated (Treated Organopoly- Organopolysiloxane)siloxan'e) It will be seen from the above that by the addition oftin-silicon compounds of the type described, the lubricatingcharacteristics, as well as the oxidation resistance oforganopolysiloxanes can be substantially improved. It will beunderstood, of course, that other concentrations of the additivesdescribed above may be employed without departing from the spirit andscope of the invention. It will also be apparent that otherorganopolysiloxanes including those in the referenced patents may beused with the additives to obtain improved high temperature lubricatingcharacteristics.

The additives of the present invention are desirable as additions notonly to organopolysiloxane type materials but to other materials such asmineral oils, vegetable oils and synthetic lubricants. For example, when3% by weight of the additive was added to the materials shown in TableIV below with the material being tested in a four-ball tester rotatingat 1200 r.p.m. at 212 degrees, scars of the dimension shown in the tablewere obtained.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A lubricating composition having improved lubricating characteristicsconsisting essentially of (1) a lubrieating material selected from thegroup consisting of mineral oils and organopolysiloxane oils and (2)from 1 to 10% by weight based on (1) of a tin-carbonsilicon-containingcompound of the formula:

L it it III ll.

where R and R are selected from the class consisting of lower alkylgroups, aryl groups, aralkyl groups, alkaryl groups, alicyclic groupsand chlorophenyl groups, and, in the case of R, mixtures of the abovegroups, and n is equal to a number up to about 1000.

2. A lubricating composition for use under heavy load at elevatedtemperatures consisting essentially of (1) a lubricating materialselected from the group consisting of mineral oils andorganopolysiloxane oils, and (2) from about 1 to 10 percent based on theweight of (1) of a tin-carbon-silicon-containing compound of theformula:

where R and R are selected from the class consisting of lower alkylgroups, aryl groups, aralkyl groups, alkaryl groups, alicyclic groups,and chlorophenyl groups, and, in the case of R, mixtures thereof, and nis equal to about 20.

4. A lubricating composition for use under heavy load at elevatedtemperatures consisting essentially of (1) a liquid organopolysiloxanehaving an average of about 1.98 to 2.25 organic groups per silicon atom,and (2) from about 1 to 10 percent by weight based upon the weight of(l) of a tin-carbon-silicon-containing compound of the formula:

F ii i i i'l -0S1CSnCSi- L in; iv I'LL where R and R are selected fromthe class consisting of lower alkyl groups, aryl groups, aralkyl groups,alkaryl '7 groups, alicyclic groups, and chlorophenyl groups, and, inthe case of R, mixtures of the above groups, and n is a number up toabout 1000.

5. A lubricating composition for use under heavy load at elevatedtemperatures consisting essentially of (1) a liquid organopolysiloxanehaving an average of about 1.98 to 2.25 organic groups per silicon atom,and (2) from 1 to percent by weight, based on the weight of (1) of atin-carbon-silicon-containing compound of the formula:

I i i i i --O---SiCSn-CSl I. it it i it 1U. where R and R are selectedfrom the class consisting of lower alkyl groups, aryl groups, aralkylgroups, alkaryl groups, alicyclic and chlorophenyl groups and, in thecase of R, mixtures of the above groups and n is a number equal to fromto 40.

6. A lubricating composition for use under heavy load at elevatedtemperatures consisting essentially of (1) a liquid organopolysiloxanehaving an average of about 1.98 to 2.25 organic groups per silicon atomand (2) from about 1 to 10 percent based on the weight of (1) of atin-carbon-silicon-containing compound of the formula:

L it 1'1 is 1'1 I'LL where R and R are selected from the classconsisting of lower alkyl groups, aryl groups, aralkyl groups, alkarylgroups, alicyclic groups and chlorophenyl groups, and, in the case of R,mixtures of the above groups and n is equal to about 20.

7. A lubricating composition for use under heavy load at elevatedtemperatures consisting essentially of (1) a liquidmethylchlorophenylpolysiloxane having an average of about 1.98 to 2.25organic groups per silicon atom and (2) from about 1 to 10 percent byweight based on the weight of (1) of a tin-carbon-silicon-containingcompound of the formula:

. L it a 1's 1 1'11,

where R and R are selected from the class consisting of lower alkylgroups, aryl groups, aralkyl groups, alkaryl groups, alicyclicgroups,and chlorophenyl groups, and, in the case of R, mixtures of the abovegroups, and n is a number up to about 1000.

8. A lubricating composition for use under heavy load at elevatedtemperatures consisting essentially of 1) a liquid polymericmethylchlorophenylsiloxane having an average of about 1.98 to 2.25organic groups per silicon atom, and (2) from about l to 10 percent, byweight, based on the weight of (1) of a tin-carbon-silicon-containingcompound of the formula:

Listens].

based on the weight of (1) of a tin-carbon-silicon-containing compoundof the formula:

F iii O-Si-O-Su-l L teeth].

where R and R are selected from the class consisting of lower alkylgroups, aryl groups, aralkyl groups, alkaryl groups, alicyclic groupsand chlorophenyl groups, and, in the case of R, mixtures of the abovegroups, and n is equal to about 20.

10. A lubricating composition having improved lubricatingcharacteristics consisting essentially of (1) a lubricating materialselected from the class consisting of mineral oils andorganopolysiloxane oils and (2) about 3% by weight based on (1) of atin-carbon-silicon-containing compound of the formula:

R H R H R j i E I I I OSi Sn--CSl- It A it 1 1 ii. where R and R areselected from the class consisting of lower alkyl groups, aryl groups,aralkyl groups, alkaryl groups, alicyclic groups and chlorophenyl groupsand, in the case of R, mixtures of the above groups, and n is equal to anumber up to about 1000.

References Cited in the file of this patent Organosilicon CompoundsContaining Tin, Papetti et al., J. Org, Chem., vol. 22, pages 526-8, May1957.

1. A LUBRICATING COMPOSITION HAVING IMPROVED LUBRICATING CHARACTERISTICSCONSISTING ESSENTIALLY OF (1) A LUBRICATING MATERIAL SELECTED FROM THEGROUP CONSISTING OF MINERAL OILS AND ORGANOPOLYSILOXANE OILS AND (2)FROM 1 TO 10% BY WEIGHT BASED ON (1) OF A TIN-CARBONSILICON-CONTAININGCOMPOUND OF THE FORMULA: